A Low Power, Low Noise and Reconfigurable Readout Circuit for Physiological Biomarkers

This work presents the design and performance verification of an ultra-low power and low noise sensor front-end circuit for biopotential signal acquisition or biosensor interfacing. The circuit consists of an input switching matrix for selecting the input sensing mode, a high gain and high common-mode rejection ratio instrumentation amplifier incorporating a fully differential input/output stage built upon a second-generation current conveyor pair and a differential bandpass filter section for post amplification and band limiting. A current mode bandgap reference utilizing subthreshold MOS devices and tunable MOS pseudoresistors provides the biasing voltages that exhibit high power supply ripple rejection. The readout circuit core has a noise efficiency factor of 2.52 while exhibiting a high differential gain and common-mode rejection ratio of 91 dB and 154 dB, respectively. The circuit dissipates around
$2\ \mu \mathrm{W}$
of power under a single supply rail of 1V. The circuit has been designed using TSMC
$0.18\ \mu\mathrm{m}$
technology whose model file parameters are obtained from MOSIS. The circuit finds application in either wearable or implantable devices.